Manufacture of viscose solutions



- cellulose by process the cellulose material capable of wxmnm romanDeanna,

OF LONDON, ENGLAND.

KANUFACTUBE 0F VISCOSE SOLUTIONS.

No Drawing.

T call whom it may concern:

WILLIAM I PORTER Be it known that I, DREAPER, a subjectof the Britain,residing invented new the Manufacture of Visco which the following isApplication filed N Specification of Letters Patent.

King of Great at London, England, have and useful Improvements in seSolutions, of

a specification.

In the usual production of solutions of with a solution of causticconcentration and then what is known as, the viscose is first treatedsoda of suitable finally treated with the requisite amount of carbondisulphide to form a cellulosexanthate which is finally dissolved inWater in such a tion containing the said tained.

In this way that a soluxanthate is obmanufacture certain diflicultiesare met with in practice which are concerned with the uneven actlon ofthe caustic soda on the cellulose materi 1. This leads to correspondinginequalities for the production parent films. of regenerated I now findthat more s tions may be obtained by which may in the. solution beparticularly cellulose. atisfactory soluworking in the mannerhereinafter described, by which means a more certain and equalize actionof the caustic soda can be obtained, with the result that the solutionof c ellulose xanthate obtained is more regular and more free fromjellified particles, which when present cause considerable difficulties.in give less perfect} products.

properly from such a solution is also procedure and When prepared theregenerated cellulose obtained of better quality and is nearer in itschemical composition to ordinary cellulose silk or films madeConsequently artificial from the same are stronger and moresatisfactory. Also satisfactory solutions may forms of cellulose whichobtained from are difiicultly dealt with under ordinary conditions.

To carry out my invention, the cellulose material is introduced intobeing closed made gas tight and will if a vacuum. In all cases tion at alow temperature a vessel which is so that it can be required sustain acaustic alkali soluwhich is below 5 C. and preferably about 0 C.-is runon to the cellulose mass in completely covers or wets tain advantagesare secured treatment and there is less such a way that it the latter.Cerby this modified swelling of the ovember 14, i 1921.

losemass. d that there is 'lulose molecule or aggregate'when the caus-Patented May 30, 1922.

Serial No. 515,157.

. Before this .low temperature caustic soda solution is brought intocontact with the cellulose material the air in the enclosing vessel maybe evacuated. The efiect of this treatment with a low temperaturecaustic alkali solution is seemingly specific and more even in its.action, possibly because'there is a slower gelatinization of the mass atthis lower temperature and therefore a better and more rapid penetrationof the solution into the cellulose mass. Both the altered swelling ofthe cellulose mass and also the reduced viscosity of the final solutionof the Xanthate indicate a more satisfactory and even action duringmereerizing.

In practice the solution of caustic alkali may be brought to atemperature of -2 C. before it comes into contact with the cellu- Theeffect obtained indicates less breaking down of the celtic alkalisolution treatment is ractised in the manner indicated and a xanthatesolution prepared from the same.

In the place of a vacuum the containing vessel may be filled with a gaswhich is either soluble in the alkali solution or reacts with the samechemically. Thus in the first instance ammonia gas may be used or in thesecond case sulphur dioxide as these may be considered as examples ofthe two types of gases mentioned. The cooled caustic soda solution isthen allowed to run over or through the cellulose mass, and in this casethere is less chance of oxidation of the cellulose mass as this isconverted into the mercerized or. alkali cellulose product. If theamount of such gas present in the said containin vessel is excessivethis may be reduced y partial evacuation of the same before the cooledsolution is allowed to come in contact with the cellulose material.

It isknown that cellulose has been subyxected to the action. of a vacuumbefore it as been mercerized. The special effect obtained in thisinvention is due to the action ofthe low temperature caustic soda oralkali solution.

What I claim is 1. The preparation of a xanthate solution by firstremoving air from a cellulose mass,

has been removed 'with a caustic alkali solution at a temperature ofbelow five degrees and afterwards treating it with carbon disulphide.

2. The preparation of a Xanthate solution y first displacing air from acellulose mass y means of another gaseous fluid, then treating thecellulose mass with a caustic alkali solution at a temperature of. belowfive degrees and afterwards treating it with carbon disulphide. I, I v

The preparatlon of a xantllate solution by treating a cellulose materialwith a caustic alkali solution at stantially 0 C., and afterwardstreating it with carbon disulphide.

4. In the temperature not exceeding 5 C.

WILLIAM PORTER DREAPER. Witnesses: JAMES C. MCRAE, HENRY'J. GREGORY.

a temperature of sub-

